The electromagnetic relay of the present invention is of a small size, for example 32.times.35.times.32 mm, wherein an assembly of elements of the electromagnetic relay, such as an electromagnet, an armature, a card, a movable contact carried on a movable contact spring, a fixed contact carried on a fixed contact spring, and a restoring spring, is encased in a housing formed by a plastic base block and a plastic cover.
A prior art structure for fixing one of the springs of the electromagnetic relay, for example, the restoring spring, to the base block is illustrated in FIG. 1. The electromagnetic relay of FIG. 1 comprises a plastic base block 1', a restoring spring 2', a movable contact spring 3', a fixed contact spring 4', a card 5', an armature 6' and an electromagnet 7'. The electromagnet 7' comprises a core 73', a bobbin 72', a coil 71' and a yoke 74'.
The two terminal conductors (not shown) of the coil 71', the terminal conductor 32' of the movable contact spring 3', and the terminal conductor 42' of the fixed contact spring 4' penetrate through the corresponding apertures of the base block 1' so that the structure of the electromagnet is coupled to the base block 1'. Also, in order to ensure the fixing of the restoring spring 2' to the base block 1', one end of the restoring spring 2' is pressed into a slot 111' in the cubic corner protrusion 11' of the base block 1'.
However, in the prior art structure of FIG. 1, there is a problem in that the restoring spring 2' is not sufficiently firmly fixed to the cubic corner protrusion 11', because such a mere pressing of the restoring spring 2' into the slot 111' cannot achieve a firm holding of the restoring spring 2' by the cubic corner protrusion 11'. This is because, when the restoring spring 2' is subjected to frequent spring action or is subjected to vibrations, the restoring spring inevitably becomes loosened from the cubic corner protrusion 111'.
In the structure of FIG. 1, the thickness of the restoring spring 2' cannot be thicker than a predetermined thickness, due to the design requirements of the electromagnetic relay, while the gap length of the slot 111' cannot be smaller than a predetermined length due to the plastic moulding process requirements. Under these circumstances, in the prior art structure, a restoring spring is constructed in which the thickness of the end portion corresponding to the slot of the cubic corner protrusion is larger than the thickness of the rest of the restoring spring or in which a depression is formed by a shock-pressing process near the end portion of the restoring spring corresponding to the slot of the cubic corner protrusion causing the effective thickness of the end portion to be increased, so as to make the thickness of the end portion of the restoring spring match the width of the gap of the slot in the cubic corner protrusion.
However, there is also another problem in that the manufacture of such a restoring spring, consisting of portions having different thicknesses, increases the cost of the production of the device and in that the fixing of the restoring spring, having such a depression in the end portion, to the slot of the cubic corner protrusion does not provide a completely firm fixing there between.